Light emitting diode and method of fabricating the same

ABSTRACT

A light emitting diode includes light emitting cells disposed on a substrate and interconnections connecting the light emitting cells to each other. Each of the light emitting cells includes a first semiconductor layer, a second semiconductor layer, an active layer disposed between the first semiconductor layer and the second semiconductor layer, and a transparent electrode layer disposed on the second semiconductor layer, wherein the first and second semiconductor layers have different conductivity types. The interconnections include a common cathode commonly connecting first and second light emitting cells of the light emitting cells, the first and second light emitting cells share the first semiconductor layer, the transparent electrode layer is continuously disposed between the first and second light emitting cells, and the common cathode is electrically connected to the first and second light emitting cells through the transparent electrode layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.14/135,925, filed on Dec. 20, 2013, and claims priority from and thebenefit of Korean Patent Application Nos. 10-2012-0150388, filed on Dec.21, 2012, 10-2013-0029136, filed on Mar. 19, 2013, 10-2013-0032481,filed on Mar. 27, 2013, 10-2013-0097078, filed on Aug. 16, 2013,10-2013-0097079, filed on Aug. 16, 2013, and 10-2014-0103815, filed onAug. 11, 2014, which are hereby incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND

1. Field

The present invention relates to a light emitting diode and a method offabricating the same, and more particularly, to a light emitting diodeincluding a plurality of light emitting cells connected to each othervia interconnections on a single substrate, and a method of fabricatingthe same.

2. Discussion of the Background

Gallium nitride (GaN) based light emitting diodes (LEDs) have been usedin a wide range of applications including full color LED displays, LEDtraffic sign boards, white LEDs, etc. In recent years, with higherluminous efficacy than existing fluorescent lamps, white light emittingdiodes are expected to overtake existing fluorescent lamps in the fieldof general lighting.

A light emitting diode may be driven to emit light by forward currentand require a supply of direct current. Thus, when the light emittingdiode is directly connected to an alternating current (AC) source, thelight emitting diode repeats on/off operation dependent upon a directionof electric current, and cannot continuously emit light and may beeasily damaged by reverse current.

To solve such problems of a light emitting diode, WO 2004/023568 (Al) ofSakai et. al., entitled “LIGHT-EMITTING DEVICE HAVING LIGHT-EMITTINGELEMENTS”, discloses a light emitting diode which can be used throughdirect connection to a high voltage AC source.

The AC light emitting diode of WO 2004/023568(Al) includes a pluralityof light emitting elements connected to each other via an air bridgeinterconnection to be driven by an AC source. Such an air-bridgeinterconnection may be easily broken by external force and may causeshort circuit due to deformation by external force.

To solve such a drawback of the air bridge interconnection, AC lightemitting diodes are disclosed in Korean Patent Nos. 10-069023 and10-1186684, for example.

FIG. 1 is a schematic plan view of a typical light emitting diodeincluding a plurality of light emitting cells, and FIG. 2 and FIG. 3 aresectional views taken along line A-A of FIG. 1.

Referring to FIG. 1 and FIG. 2, the light emitting diode includes asubstrate 21, a plurality of light emitting cells 26 including S1, S2, atransparent electrode layer 31, an insulation layer 33, and aninterconnection 35. In addition, each of the light emitting cells 26includes a lower semiconductor layer 25, an active layer 27, and anupper semiconductor layer 29, and a buffer layer 23 may be interposedbetween the substrate 21 and the light emitting cells 26.

The light emitting cells 26 are formed by patterning the lowersemiconductor layer 25, active layer 27, and upper semiconductor layer29 grown on the substrate 21, and the transparent electrode layer 31 isformed on each of the light emitting cells S1, S2. In each of the lightemitting cells 26, an upper surface of the lower semiconductor layer 25is partially exposed by partially removing the active layer 27 and theupper semiconductor layer 29 for connection to the interconnection 35.

Next, the insulation layer 33 is formed to cover the light emittingcells 26. The insulation layer 33 includes a side insulation layer 33 acovering side surfaces of the light emitting cells 26 and an insulationprotective layer 33 b covering the transparent electrode layer 31. Theinsulation layer 33 is formed with an opening through which a portion ofthe transparent electrode layer 31 is exposed and an opening throughwhich the lower semiconductor layer 25 is exposed. Then, theinterconnection 35 is formed on the insulation layer 33, in which afirst connection section 35 p of the interconnection 35 is connected tothe transparent electrode layer 31 of one light emitting cell S1 throughthe opening of the insulation layer 33, and a second connection section35 n of the interconnection 35 is connected to the lower semiconductorlayer 25 of another light emitting cell S2 adjacent the one lightemitting cell S1 through the other opening of the insulation layer 33.The second connection section 35 n is connected to an upper surface ofthe lower semiconductor layer 25, which is exposed by partially removingthe active layer 27 and the upper semiconductor layer 29.

In a conventional technique, the interconnection 35 is formed on theinsulation layer 33 and thus may be prevented from deformation byexternal force. In addition, since the interconnection 35 is separatedfrom the light emitting cells 26 by the side insulation layer 33 a, itis possible to prevent short circuit of the light emitting cells 26 bythe interconnection 35.

However, such a conventional light emitting diode may have a limit incurrent spreading in areas of the light emitting cells 26. Specifically,electric current may be concentrated under one end of theinterconnection 35 connected to the transparent electrode layer 31instead of being evenly spread in the areas of the light emitting cells26. Current crowding may become severe with increasing current density.

Moreover, such a conventional light emitting diode may have problems inthat some of the light generated in the active layer 27 may be absorbedand lost by the interconnection 35, and the thickness of the insulationlayer 33 may need to be increased to prevent formation of defects suchas pin-holes and the like.

Furthermore, since a portion of the upper surface of the lowersemiconductor layer 25 is exposed for electric connection of the secondconnection section 35 n, the active layer 27 and the upper semiconductorlayer 29 are partially removed, and may thereby reduce an effectivelight emitting area.

In order to prevent current crowding, a current blocking layer 30 may bedisposed between the transparent electrode layer 31 and the lightemitting cells 26 to prevent current crowding under the connection endof the interconnection 35.

FIG. 3 is a sectional view of a light emitting diode including a currentblocking layer 30 in the related art.

Referring to FIG. 1 and FIG. 3, the current blocking layer 30 isdisposed under the connection end of the interconnection 35, and maythereby prevent current crowding under the connection end of theinterconnection 35. In addition, the current blocking layer 30 may beformed as a reflector such as a distributed Bragg reflector, and maythereby prevent light generated in the active layer 27 from beingabsorbed into the connection end of the interconnection 35.

However, when the current blocking layer 30 is additionally formed asshown in FIG. 3, a photolithography process for forming the currentblocking layer 30 is added, and may thereby increase manufacturingcosts.

Moreover, as in the light emitting diode of FIG. 2, the light emittingdiode of FIG. 3 may also have problems, such as optical loss due toabsorption of light generated in the active layer 27 by theinterconnection 35, reduction in effective light emitting area, andincrease in thickness of the insulation layer 33 to prevent defects suchas pinholes in the insulation layer 33.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a light emittingdiode, which may employ a current blocking layer while preventingincrease in the number of photolithography processes, and a method offabricating the same.

Exemplary embodiments of the present invention also provide a lightemitting diode capable of reducing absorption of light by aninterconnection, and a method of fabricating the same.

Exemplary embodiments of the present invention also provide a lightemitting diode, which includes a plurality of light emitting cells eachhaving an increased effective light emitting area, and a method offabricating the same.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

An exemplary embodiment of the present invention provides a lightemitting diode, the light emitting diode including a first lightemitting cell and a second light emitting cell disposed on a substrateand spaced apart from each other, a first transparent electrode layerdisposed on the first light emitting cell and electrically connected tothe first light emitting cell, a current blocking layer disposed betweena portion of the first light emitting cell and the first transparentelectrode layer, an interconnection electrically connecting the firstlight emitting cell and the second light emitting cell, and aninsulation layer disposed between the interconnection and a side surfaceof the first light emitting cell. The current blocking layer and theinsulation layer are connected to each other.

Thus, the insulation layer separating the interconnection from the sidesurface of the light emitting cell may be formed together with thecurrent blocking layer by the same process. Since the insulation layeris formed together with the current blocking layer, there may be no needfor formation of the insulation layer together with an insulationprotective layer as in the related art, thereby allowing the insulationprotective layer and the interconnection to be formed using the samemask.

In addition, the current blocking layer and the insulation layer mayinclude distributed Bragg reflectors. Thus, the light emitting diode maysignificantly reduce an amount of light absorbed by the interconnection.Further, the insulation layer is formed as a distributed Bragg reflectorformed of multiple layers, thereby efficiently preventing formation ofdefects such as pinholes.

Further, the current blocking layer and the insulation layer may bedisposed between the first light emitting cell and the interconnectionover an entire overlapping area between the first light emitting celland the interconnection.

Further, the insulation layer may be disposed between theinterconnection and the side surface of the second light emitting cell.

The light emitting diode may further include an insulation protectivelayer disposed on the first light emitting cell and the second lightemitting cell. The insulation protective layer is disposed outside anarea in which the interconnection is formed. In addition, a side surfaceof the insulation protective layer may face a side surface of theinterconnection on a coplanar surface. The side surface of theinsulation protective layer may contact the side surface of theinterconnection. The side surface of the insulation protective layer maybe spaced apart from the side surface of the interconnection.

In some embodiments, the light emitting diode may further include afirst transparent conductive layer disposed between the insulation layerand the interconnection. In addition, the first transparent conductivelayer may be connected to the first transparent electrode layer.Further, the first transparent conductive layer may be formed of thesame material as that of the first transparent electrode layer.

Each of the first and second light emitting cells may include a lowersemiconductor layer, an upper semiconductor layer, and an active layerdisposed between the lower semiconductor layer and the uppersemiconductor layer. The first transparent electrode layer iselectrically connected to the upper semiconductor layer, and theinterconnection is electrically connected at one end thereof to thefirst transparent electrode layer and at the other end thereof to thelower semiconductor layer of the second light emitting cell. Here, eachof the lower semiconductor layer, active layer and upper semiconductorlayer may include a gallium nitride-based semiconductor layer. The lowersemiconductor layer and the upper semiconductor layer may be n-type andp-type semiconductor layers, respectively, or vice versa.

The interconnection may be directly connected to the first transparentelectrode layer over an entire overlapping area there between.Accordingly, as compared with techniques in the related art, the lightemitting diode according to the present invention may increase aconnection area between the interconnection and the first transparentelectrode layer, or may decrease an area of the interconnection disposedon the first transparent electrode layer.

The current blocking layer may be disposed at least under the connectionarea between the first transparent electrode layer and theinterconnection. As a result, it is possible to prevent current crowdingunder the connection area of the interconnection.

In addition, the first light emitting cell and the second light emittingcell may have the same structure.

An exemplary embodiment of the present invention provides a lightemitting diode, the light emitting diode including a first lightemitting cell and a second light emitting cell disposed on a substrateand spaced apart from each other, a first transparent electrode layerdisposed on the first light emitting cell and electrically connected tothe first light emitting cell, a current blocking layer disposed betweena portion of the first light emitting cell and the first transparentelectrode layer, an interconnection electrically connecting the firstlight emitting cell to the second light emitting cell, and an insulationlayer spaced apart from the interconnection from a side surface of thefirst light emitting cell. The current blocking layer and the insulationlayer include distributed Bragg reflectors having the same structure andformed of the same material. Thus, the current blocking layer and theinsulation layer may be simultaneously formed by the same process.

In addition, the interconnection may be directly connected to the firsttransparent electrode layer over an entire overlapping areatherebetween.

The distributed Bragg reflectors may be disposed under theinterconnection over the entire area of the interconnection.

The light emitting diode may further include an insulation protectivelayer disposed outside an area in which the interconnection is formed.

In some embodiments, the light emitting diode may further include afirst transparent conductive layer disposed between the insulation layerand the interconnection. In addition, the first transparent conductivelayer may be connected to the first transparent electrode layer.Further, the first transparent conductive layer may electrically connectthe first transparent electrode layer to the second light emitting cell.

An exemplary embodiment of the present invention provides a lightemitting diode including a first light emitting cell and a second lightemitting cell disposed on a substrate and spaced apart from each other,a first transparent electrode layer disposed on the first light emittingcell and electrically connected to the first light emitting cell, acurrent blocking layer disposed between a portion of the first lightemitting cell and the first transparent electrode layer, aninterconnection electrically connecting the first light emitting cell tothe second light emitting cell, and an insulation layer separating theinterconnection from a side surface of the first light emitting cell. Inaddition, the second light emitting cell has an inclined side surface,the interconnection includes a first connection section connected to thefirst light emitting cell and a second connection section connected tothe second light emitting cell, in which the first connection sectioncontacts the first transparent electrode layer within an upper area ofthe current blocking layer and the second connection section contactsthe inclined side surface of the second light emitting cell.

Exemplary embodiments of the invention provide a light emitting diodewhich allows a current blocking layer and a side insulation layer to beformed by the same process. Since the current blocking layer and theside insulation layer are formed by the same process, it is possible toprevent addition of an exposure process even in the case of adopting thecurrent blocking layer. In addition, the current blocking layer and theinsulation layer are formed as the distributed Bragg reflectors, therebyminimizing absorption of light by the interconnection.

Further, one of the connection sections of the interconnection iselectrically connected to an inclined side surface of the light emittingcell, whereby an effective light emitting area of the light emittingcell can be increased. In addition, since the current blocking layer andthe side insulation layer are formed by the same process, it is possibleto prevent addition of an exposure process even in the case of adoptingthe current blocking layer. Further, the current blocking layer and theinsulation layer are formed as the distributed Bragg reflectors, therebyminimizing absorption of light by the interconnection.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a schematic plan view of a light emitting diode in the relatedart.

FIG. 2 and FIG. 3 are schematic sectional views taken along line A-A ofFIG. 1.

FIG. 4 is a schematic sectional view of a light emitting diode accordingto an exemplary embodiment of the present invention.

FIG. 5 to FIG. 11 are schematic sectional views illustrating a method offabricating a light emitting diode according to the exemplary embodimentof FIG. 4.

FIG. 12 is a schematic sectional view of a light emitting diodeaccording to an exemplary embodiment of the present invention.

FIG. 13 to FIG. 16 are schematic sectional views illustrating a methodof fabricating a light emitting diode according to the exemplaryembodiment of FIG. 12.

FIG. 17 is a schematic plan view of a light emitting diode according toan exemplary embodiment of the present invention.

FIG. 18 is a schematic sectional view taken along line B-B of FIG. 17.

FIG. 19 to FIG. 25 are schematic sectional views illustrating a methodof fabricating a light emitting diode according to the exemplaryembodiment of FIG. 18.

FIG. 26 is a schematic plan view of a light emitting diode according toan exemplary embodiment of the present invention.

FIG. 27 to FIG. 30 are schematic sectional views illustrating a methodof fabricating a light emitting diode according to the exemplaryembodiment of FIG. 26.

FIG. 31 is a schematic plan view of a light emitting diode according toan exemplary embodiment of the present invention.

FIG. 32 is a schematic sectional view taken along line B-B of FIG. 31.

FIG. 33 to FIG. 37 are schematic sectional views illustrating a methodof fabricating a light emitting diode according to the exemplaryembodiment of FIG. 31.

FIG. 38 is a schematic sectional view of a light emitting diodeaccording to an exemplary embodiment of the present invention.

FIG. 39 is a schematic sectional view taken along line B-B of FIG. 38.

FIG. 40 is a schematic plan view of a light emitting diode according toan exemplary embodiment of the present invention.

FIG. 41 a and FIG. 41 b are sectional views taken along lines A-A andB-B of FIG. 40.

FIG. 42 is a schematic circuit diagram of the light emitting diode ofFIG. 40.

FIG. 43 is a schematic circuit diagram illustrating a light emittingdiode according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which embodiments of the invention are shown.This invention may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure isthorough, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, the size and relative sizes oflayers and regions may be exaggerated for clarity. Like referencenumerals in the drawings denote like elements.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent. It will be understood that for the purposes of this disclosure,“at least one of X, Y, and Z” can be construed as X only, Y only, Zonly, or any combination of two or more items X, Y, and Z (e.g., XYZ,XYY, YZ, ZZ).

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

FIG. 4 is a schematic sectional view of a light emitting diode accordingto an exemplary embodiment of the present invention.

Referring to FIG. 4, a light emitting diode according to one embodimentof the invention includes a substrate 51, light emitting cells S1, S2, atransparent electrode layer 61, a current blocking layer 60 a, aninsulation layer 60 b, an insulation protective layer 63, and aninterconnection 65. The light emitting diode may further include abuffer layer 53.

The substrate 51 may be an insulating or conductive substrate. Forexample, the substrate 51 may be a sapphire substrate, a gallium nitridesubstrate, a silicon carbide (SiC) substrate, or a silicon substrate. Ona single substrate 51, the first light emitting cell S1 and the secondlight emitting cell S2 are separated from each other. Each of the firstand second light emitting cells S1, S2 has a stack structure 56, whichincludes a lower semiconductor layer 55, an upper semiconductor layer 59disposed on one area of the lower semiconductor layer, and an activelayer 57 interposed between the lower semiconductor layer and the uppersemiconductor layer. Here, the upper and lower semiconductor layers maybe p-type and n-type semiconductor layers, respectively, or vice versa.

Each of the lower semiconductor layer 55, the active layer 57 and theupper semiconductor layer 59 may be formed of a gallium nitride-basedmaterial, for example, (Al, In, Ga)N. The active layer 57 may be formedof a material having a composition capable of emitting light in adesired wavelength range, for example, UV or blue light, and the lowerand upper semiconductor layers 55, 59 are formed of a material having awider band gap than that of the active layer 57.

As shown, the lower semiconductor layer 55 and/or the uppersemiconductor layer 59 may be formed of a single layer or multiplelayers. In addition, the active layer 57 may have a single quantum-wellstructure or a multi-quantum well structure.

Each of the first and second light emitting cells S1, S2 may have aninclined side surface, an inclined angle of which ranges from 15° to 80°with respect to an upper surface of the substrate 51. Although notshown, the lower semiconductor layer 55 may have a stepped portionformed along a sidewall thereof.

The active layer 57 and the upper semiconductor layer 59 are disposed onsome area of the lower semiconductor layer 55, and the other area of thelower semiconductor layer 55 is exposed as shown in FIG. 4. Although theside surfaces of the active layer 57 and upper semiconductor layer 57are shown as being vertical side surfaces in FIG. 4, it should beunderstood that these side surfaces may also be inclined.

In FIG. 4, the first light emitting cell S1 and the second lightemitting cell S2 are partially shown. However, it should be noted thatthe first light emitting cell S1 and the second light emitting cell S2have a similar or the same structure. Specifically, the first and secondlight emitting cells S1, S2 have the same stack structure, and some areaof the lower semiconductor layer 55 of the first light emitting cell S1is exposed as in some area of the lower semiconductor layer 55 of thesecond light emitting cell S2.

The buffer layer 53 may be interposed between the light emitting cellsS1, S2 and the substrate 51. The buffer layer 53 is used to relievelattice mismatch between the substrate 51 and the lower semiconductorlayer 55 when the substrate 51 is a growth substrate.

The transparent electrode layer 61 is disposed on each of the lightemitting cells S1, S2. Specifically, a first transparent electrode layer61 is disposed on the first light emitting cell S1, and a secondtransparent electrode layer 61 is disposed on the second light emittingcell S2. The transparent electrode layer 61 may be disposed on an uppersurface of the upper semiconductor layer 59 to be connected to the uppersemiconductor layer 59, and may have a smaller area than that of theupper semiconductor layer 59. In other words, the transparent electrodelayer 61 may be recessed from an edge of the upper semiconductor layer59. Thus, the light emitting diode according to this embodiment mayprevent current crowding at the edge of the transparent electrode layer61 through the sidewalls of the light emitting cells S1, S2.

The current blocking layer 60 a may be disposed on each of the lightemitting cells S1, S2 between the transparent electrode layer 61 andeach of the light emitting cells S1, S2. Particularly, the currentblocking layer 60 a is disposed near one edge of the first lightemitting cell S1, and a portion of the transparent electrode layer 61 isdisposed on the current blocking layer 60 a. The current blocking layer60 a is formed of an insulation material, and particularly, may includea distributed Bragg reflector formed by alternately stacking layershaving different indices of refraction.

The insulation layer 60 b covers a portion of the side surface of thefirst light emitting cell S1. As shown in FIG. 4, the insulation layer60 b extends to cover a portion of a side surface of the lowersemiconductor layer 55 of the second light emitting cell S2. Theinsulation layer 60 b has the same structure as that of the currentblocking layer 60 a and is formed of the same material as that of thecurrent blocking layer 60 a, and may include a distributed Braggreflector. When the insulation layer 60 b includes the distributed Braggreflector formed of multiple layers, it is possible to efficientlysuppress formation of defects such as pinholes in the insulation layer60 b. Alternatively, the insulation layer 60 b may be separated from thecurrent blocking layer 60 a.

The interconnection 65 electrically connects the first light emittingcell S1 to the second light emitting cell S2. The interconnection 65 iselectrically connected at one end thereof to the transparent electrodelayer 61 on the first light emitting cell S1 and at the other endthereof to the lower semiconductor layer 55 of the second light emittingcell S2, whereby the first light emitting cell S1 can be directlyconnected in series to the second light emitting cell S2.

The interconnection 65 may contact the transparent electrode layer 61over an entire overlapping area between the interconnection 65 and thetransparent electrode layer 61. In the related art, a portion of theinsulation layer 33 is disposed between the transparent electrode layer31 and the interconnection 35. However, in this embodiment, theinterconnection 65 directly contacts the transparent electrode layer 61without any insulating material interposed therebetween.

Further, the current blocking layer 60 a may be disposed over an entireoverlapping area between the interconnection 65 and the transparentelectrode layer 61, and the current blocking layer 60 a and theinsulation layer 60 b may be disposed over an entire overlapping areabetween the interconnection 65 and the first light emitting cell S1. Inaddition, the insulation layer 60 b may be disposed between the secondlight emitting cell S2 and the interconnection 65 except for aconnection area between the interconnection 65 and the second lightemitting cell S2.

When the current blocking layer 60 a and the insulation layer 60 b havereflective characteristics like distributed Bragg reflectors, thecurrent blocking layer 60 a and the insulation layer 60 b may besubstantially within the same area as that of the interconnection 65 inan area two times or less than that of the interconnection 65. Thecurrent blocking layer 60 a and the insulation layer 60 b preventabsorption of light by the interconnection 65 when light is emitted fromthe active layer 57. However, when the current blocking layer 60 a andthe insulation layer 60 b occupy an excessively large area, there is apossibility of blocking discharge of light. Thus, it may be necessary tolimit the area of the current blocking layer 60 a and the insulationlayer 60 b.

The insulation protective layer 63 may be disposed outside the area ofthe interconnection 65. The insulation protective layer 63 covers thefirst and second light emitting cells S1, S2 outside the area of theinterconnection 65. The insulation protective layer 63 may be formed ofa silicon oxide layer (SiO2) or a silicon nitride layer. The insulationprotective layer 63 is formed with an opening through which thetransparent electrode layer 61 on the first light emitting cell S1 andthe lower semiconductor layer of the second light emitting cell S2 areexposed, and the interconnection 65 may be disposed within this opening.

A side surface of the insulation protective layer 63 and a side surfaceof the interconnection 65 may be disposed to face each other, or tocontact each other. Alternatively, the side surface of the insulationprotective layer 63 may be separated from the side surface of theinterconnection 65 to face each other.

According to this embodiment, the current blocking layer 60 a and theinsulation layer 60 b may be formed of the same material and have thesame structure, and thus may be formed by the same process. In addition,since the interconnection 65 is disposed within the opening of theinsulation protective layer 63, the insulation protective layer 63 andthe interconnection 65 may be formed using the same mask pattern.

In this embodiment, the light emitting diode is illustrated as includingtwo light emitting cells, that is, the first light emitting cell S1 andthe second light emitting cell S2. However, the present invention is notlimited to the two light emitting cells, and more light emitting cellsmay be electrically connected to each other by interconnections 65. Forexample, the interconnections 65 may electrically connect the lowersemiconductor layers 55 of adjacent light emitting cells to thetransparent electrode layers 61 thereof to form a series array of thelight emitting cells. The light emitting diode according to thisembodiment may include a plurality of such arrays, which is connected toeach other in reverse parallel and connected to an AC source. Inaddition, the light emitting diode may be provided with a bridgerectifier (not shown) connected to the series array of light emittingcells, such that the light emitting cells can be driven by an AC source.The bridge rectifier may be formed by connecting the light emittingcells having the same structure as that of the light emitting cells S1,S2 using the interconnections 65.

FIG. 5 to FIG. 11 are sectional views illustrating a method offabricating a light emitting diode according to one embodiment of thepresent invention.

Referring to FIG. 5, a semiconductor stack structure 56 is formed on asubstrate 51, and includes a lower semiconductor layer 55, an activelayer 57 and an upper semiconductor layer 59. In addition, beforeformation of the lower semiconductor layer 55, a buffer layer 53 may beformed on the substrate 51.

The substrate 51 may be a sapphire (Al2O3) substrate, a silicon carbide(SiC) substrate, a zinc oxide (ZnO) substrate, a silicon (Si) substrate,a gallium arsenide (GaAs), a gallium phosphide (GaP) substrate, alithium alumina (LiAl2O3) substrate, a boron nitride (BN) substrate, analuminum nitride (AlN) substrate, or a gallium nitride (GaN) substrate,without being limited thereto. That is, the substrate 51 may be selectedfrom among various materials dependent upon materials of semiconductorlayers to be formed thereon.

The buffer layer 53 is formed to relieve lattice mismatch between thesubstrate 51 and the semiconductor layer 55 formed thereon, and may beformed of, for example, gallium nitride (GaN) or aluminum nitride (AlN).When the substrate 51 is a conductive substrate, the buffer layer 53 maybe formed as an insulation layer or a semi-insulation layer, forexample, AlN or semi-insulation GaN.

Each of the lower semiconductor layer 55, the active layer 57 and theupper semiconductor layer 59 may be formed of a gallium nitride-basedsemiconductor material, for example, (Al, In, Ga)N. The lower and uppersemiconductor layers 55, 59 and the active layer 57 may bediscontinuously or continuously formed by metal organic chemical vapordeposition (MOCVD), molecular beam epitaxy, hydride vapor phase epitaxy(HVPE), and the like.

Here, the lower and upper semiconductor layers are n-type and p-typesemiconductor layers, respectively, or vice versa. The n-typesemiconductor layer is formed by doping a gallium nitride-based compoundsemiconductor layer with, for example, silicon (Si) impurities, and thep-type semiconductor layer is formed by doping the gallium nitride-basedcompound semiconductor layer with, for example, magnesium (Mg)impurities.

Referring to FIG. 6, a plurality of light emitting cells S1, S2 isformed to be separated from each other by photolithography and etching.Each of the light emitting cells S1, S2 has an inclined side surface,and the lower semiconductor layer 55 of each of the light emitting cellsS1, S2 is partially exposed.

In each of the light emitting cells S1, S2, the lower semiconductorlayer 55 is first exposed by mesa-etching, and the light emitting cellsare separated from each other by a cell isolation process.Alternatively, the light emitting cells S1, S2 may be first separatedfrom each other by the cell isolation process, and then are subjected tomesa etching to expose the lower semiconductor layers 55 thereof.

Referring to FIG. 7, a current blocking layer 60 a covering a partialarea of the first light emitting cell S1 is formed together with aninsulation layer 60 b covering a partial area of a side surface of thefirst light emitting cell S1. The insulation layer 60 b may also extendto cover a portion of a side surface of the lower semiconductor layer 55of the second light emitting cell S2.

The current blocking layer 60 a and the insulation layer 60 b may beformed by depositing an insulation material layer, followed bypatterning the insulation material layer through photolithography andetching. Alternatively, the current blocking layer 60 a and theinsulation layer 60 b may be formed of an insulation material through alift-off process. In particular, the current blocking layer 60 a and theinsulation layer 60 b may be formed as distributed Bragg reflectors byalternately stacking layers having different indices of refraction, forexample, a SiO₂ layer and a TiO₂ layer. When the insulation layer 60 bis a distributed Bragg reflector formed of multiple layers, it ispossible to prevent formation of defects such as pinholes in theinsulation layer 60 b, whereby the insulation layer 60 b may be formedto be relatively thin as compared with conventional techniques.

As shown in FIG. 7, the current blocking layer 60 a and the insulationlayer 60 b may be connected to each other, without being limitedthereto.

Next, a transparent electrode layer 61 is formed on the first and secondlight emitting cells S1, S2. The transparent electrode layer 61 may beformed of a conductive material such as indium tin oxide (ITO) or zincoxide, or a metal layer such as Ni/Au. The transparent electrode layer61 is connected to the upper semiconductor layer 59 and is partiallydisposed on the current blocking layer 60 a. The transparent electrodelayer 61 may be formed by a lift-off process, without being limitedthereto. Alternatively, the transparent electrode layer 61 may be formedby photolithography and etching.

Referring to FIG. 8, an insulation protective layer 63 is formed tocover the first and second light emitting cells S1, S2. The insulationprotective layer 63 covers the transparent electrode layer 61 and theinsulation layer 60 b. In addition, the insulation protective layer 63may cover an overall area of the first and second light emitting cellsS1, S2. The insulation protective layer 63 may be formed as aninsulation material layer such as a silicon oxide layer or a siliconnitride layer by chemical vapor deposition or the like.

Referring to FIG. 9, a mask pattern 70 having an opening is formed onthe insulation protective layer 63. The opening of the mask pattern 70corresponds to an area of the interconnection. Next, some region of theinsulation protective layer 63 is etched using the mask pattern 70 as amask. As a result, an opening is formed in the insulation protectivelayer 63 to expose some of the transparent electrode layer 61 and theinsulation layer 60 b, and the lower semiconductor layer 55 of thesecond light emitting cell S2 therethrough.

Referring to FIG. 10, with the mask pattern 70 remaining on theinsulation protective layer 63, a conductive material is deposited toform an interconnection 65 in the opening of the mask pattern 70. Atthis point, a portion 65 a of the conductive material may be depositedon the mask pattern 70. The conductive material may be deposited byplating, electron-beam evaporation or sputtering.

Referring to FIG. 11, the mask pattern 70 is removed together with theportion 65 a of the conductive material on the mask pattern 70.Accordingly, the interconnection 65 electrically connecting the firstand second light emitting cells S1, S2 to each other is finally formed.

Here, one end of the interconnection 65 is connected to the transparentelectrode layer 61 of the first light emitting cell S1, and the otherend thereof to the lower semiconductor layer 55 of the second lightemitting cell S2. In addition, the one end of the interconnection 65 isconnected to the transparent electrode layer 60 a within an upper areaof the current blocking layer 60 a. The interconnection 65 is separatedfrom the side surface of the first light emitting cell S1 and the sidesurface of the second light emitting cell S2 via the insulation layer 60b. Furthermore, the interconnection 65 is disposed within the upper areaof the current blocking layer 60 a and the insulation layer 60 b exceptfor a portion of the interconnection 65 electrically connected to thelower semiconductor layer 55 of the second light emitting cell S2.

In this embodiment, the current blocking layer 60 a and the insulationlayer 60 b are formed by the same process. Accordingly, the insulationprotective layer 63 and the interconnection 65 may be formed using thesame mask pattern 70, whereby the light emitting diode can be fabricatedusing the same number of exposure processes while adding the currentblocking layer 60 a.

FIG. 12 is a schematic sectional view of a light emitting diodeaccording to an exemplary embodiment of the present invention.

Referring to FIG. 12, the light emitting diode according to thisembodiment is generally similar to the light emitting diode describedwith reference to FIG. 4, and further includes a transparent conductivelayer 62.

In the light emitting diode according to this embodiment, a substrate51, light emitting cells S1, S2, a buffer layer 53, a transparentelectrode layer 61, a current blocking layer 60 a, an insulation layer60 b, an insulation protective layer 63 and an interconnection 65 aresimilar to those of the light emitting diode according to the aboveembodiment described with reference to FIG. 4, and detailed descriptionsthereof will be omitted.

The transparent conductive layer 62 is disposed between the insulationlayer 60 b and the interconnection 65. The transparent conductive layer62 has a narrower line width than the insulation layer 60 b, therebypreventing short circuit of the upper semiconductor layer 59 and thelower semiconductor layer 55 due to the transparent conductive layer 62.That is, when the insulation layer 60 b is thicker than the transparentconductive layer 62, the insulation layer 60 b may prevent a shortcircuit.

On the other hand, the transparent conductive layer 62 is connected tothe first transparent electrode layer 61, and may connect the firsttransparent electrode layer 61 to the second light emitting cell S2. Forexample, one end of the transparent conductive layer 62 may beelectrically connected to the lower semiconductor layer 55 of the secondlight emitting cell. In addition, when two or more light emitting cellsare connected to each other, a second transparent conductive layer 62may extend from a second transparent electrode layer 61 on the secondlight emitting cell S2.

In this embodiment, since the transparent conductive layer 62 isdisposed between the interconnection 65 and the insulation layer 60 b,electric current can flow through the transparent conductive layer 62even in the case where the interconnection 65 is disconnected, therebyimproving electrical stability of the light emitting diode.

FIG. 13 to FIG. 16 are schematic sectional views illustrating a methodof fabricating a light emitting diode according to the present exemplaryembodiment.

Referring to FIG. 13, as in the method described with reference to FIG.5 and FIG. 6, a semiconductor stack structure 56 is formed on asubstrate 51 and a plurality of light emitting cells S1, S2 is formed tobe separated from each other via photolithography and etching. Then, asdescribed with reference to FIG. 7, a current blocking layer 60 acovering a partial area of the first light emitting cell S1 is formedtogether with an insulation layer 60 b covering a partial area of a sidesurface of the first light emitting cell S1. The insulation layer 60 bmay also extend to cover a portion of a side surface of the lowersemiconductor layer 55 of the second light emitting cell S2.

As described with reference to FIG. 7, the current blocking layer 60 aand the insulation layer 60 b may be formed as distributed Braggreflectors by alternately stacking layers having different indices ofrefraction, for example, a SiO₂ layer and a TiO₂ layer. When theinsulation layer 60 b is a distributed Bragg reflector formed ofmultiple layers, it is possible to prevent formation of defects such aspinholes in the insulation layer 60 b, whereby the insulation layer 60 bmay be formed to be relatively thin as compared with conventionaltechniques.

Next, a transparent electrode layer 61 is formed on the first and secondlight emitting cells S1, S2. As described with reference to FIG. 7, thetransparent electrode layer 61 may be formed of a conductive materialsuch as indium tin oxide (ITO) or zinc oxide, or a metal layer such asNi/Au. The transparent electrode layer 61 is connected to the uppersemiconductor layer 59 and is partially disposed on the current blockinglayer 60 a. The transparent electrode layer 61 may be formed by alift-off process, without being limited thereto. Alternatively, thetransparent electrode layer 61 may be formed by photolithography andetching.

During formation of the transparent electrode layer 61, a transparentconductive layer 62 is also formed. The transparent conductive layer 62may be formed of the same material as that of the transparent electrodelayer 61 through the same process. The transparent conductive layer 62is formed on the insulation layer 60 b, and may be connected to thetransparent electrode layer 61. Further, one end of the transparentconductive layer 62 may be electrically connected to the lowersemiconductor layer 55 of the second light emitting cell S2.

Referring to FIG. 14, an insulation protective layer 63 is formed tocover the first and second light emitting cells S1, S2. The insulationprotective layer 63 covers the transparent electrode layer 61, thetransparent conductive layer 62 and the insulation layer 60 b. Inaddition, the insulation protective layer 63 may cover an overall areaof the first and second light emitting cells S1, S2. The insulationprotective layer 63 may be formed as an insulation material layer suchas a silicon oxide layer or a silicon nitride layer by chemical vapordeposition or the like.

Referring to FIG. 15, as described with reference to FIG. 9, a maskpattern 70 having an opening is formed on the insulation protectivelayer 63. The opening of the mask pattern 70 corresponds to an area ofthe interconnection. Next, some region of the insulation protectivelayer 63 is etched using the mask pattern 70 as a mask. As a result, anopening is formed in the insulation protective layer 63 to expose someof the transparent electrode layer 61 and the transparent conductivelayer 62, and the lower semiconductor layer 55 of the second lightemitting cell S2 therethrough. Further, a portion of the insulationlayer 60 b is exposed through the opening.

Referring to FIG. 16, as described with reference to FIG. 10, with themask pattern 70 remaining on the insulation protective layer 63, aconductive material is deposited to form an interconnection 65 in theopening of the mask pattern 70.

Next, as described with reference to FIG. 11, the mask pattern 70 isremoved together with a portion 65 a of the conductive material on themask pattern 70. Accordingly, the interconnection 65 electricallyconnecting the first and second light emitting cells S1, S2 to eachother is finally formed.

In the embodiment described with reference to FIG. 5 to FIG. 11, theinsulation layer 60 b may be damaged during etching of the insulationprotective layer 63. For example, when the insulation protective layer63 is subjected to etching using an etching solution such as fluoricacid, the insulation layer 60 b including an oxide layer may be damagedby the etching solution. Thus, the insulation layer 60 b may notinsulate the interconnection 65 from the first light emitting cell S1,thereby causing short circuit.

On the contrary, in the present exemplary embodiment, since thetransparent conductive layer 62 is disposed on the insulation layer 60b, the insulation layer 60 b under the transparent conductive layer 62can be protected from etching damage. Thus, it is possible to preventshort circuit due to the interconnection 65.

In the present exemplary embodiment, the transparent electrode layer 61and the transparent conductive layer 62 may be formed by the sameprocess. Thus, the light emitting diode can be fabricated using the samenumber of exposure processes while adding the transparent conductivelayer 62.

FIG. 17 is a schematic plan view of a light emitting diode according toan exemplary embodiment of the present invention, and FIG. 18 is aschematic sectional view taken along line B-B of FIG. 17.

Referring to FIG. 17 and FIG. 18, the light emitting diode includes asubstrate 51, light emitting cells S1, S2, a transparent electrode layer61, a current blocking layer 60 a, an insulation layer 60 b, aninsulation protective layer 63, and an interconnection 65. The lightemitting diode may further include a buffer layer 53.

The substrate 51 may be an insulating or conductive substrate. Forexample, the substrate 51 may be a sapphire substrate, a gallium nitridesubstrate, a silicon carbide (SiC) substrate, or a silicon substrate. Inaddition, the substrate 51 may be a substrate having a convex-concavepattern (not shown) on an upper surface thereof, such as a patternedsapphire substrate.

On a single substrate 51, the first light emitting cell S1 and thesecond light emitting cell S2 are separated from each other. Each of thefirst and second light emitting cells S1, S2 has a stack structure 56,which includes a lower semiconductor layer 55, an upper semiconductorlayer 59 disposed on one area of the lower semiconductor layer, and anactive layer 57 interposed between the lower semiconductor layer and theupper semiconductor layer. Here, the upper and lower semiconductorlayers may be p-type and n-type semiconductor layers, respectively, orvice versa.

Each of the lower semiconductor layer 55, the active layer 57 and theupper semiconductor layer 59 may be formed of a gallium nitride-basedmaterial, for example, (Al, In, Ga)N. The active layer 57 may be formedof a material having a composition capable of emitting light in adesired wavelength range, for example, UV or blue light, and the lowerand upper semiconductor layers 55, 59 are formed of a material having awider band gap than that of the active layer 57.

As shown, the lower semiconductor layer 55 and/or the uppersemiconductor layer 59 may be formed of a single layer or multiplelayers. In addition, the active layer 57 may have a single quantum-wellstructure or a multi-quantum well structure.

Each of the first and second light emitting cells S1, S2 may have aninclined side surface, an inclined angle of which ranges from 15° to 80°with respect to an upper surface of the substrate 51.

The active layer 57 and the upper semiconductor layer 59 are disposed onthe lower semiconductor layer 55. An upper surface of the lowersemiconductor layer 55 may be completely covered by the active layer 57such that the side surface of the lower semiconductor layer 55 can beexposed.

In FIG. 18, the first light emitting cell S1 and the second lightemitting cell S2 are partially shown. However, it should be noted thatthe first light emitting cell S1 and the second light emitting cell S2have a similar or the same structure as shown in FIG. 17. Specifically,the first and second light emitting cells S1, S2 have the same galliumnitride-based semiconductor stack structure, and may have inclined sidesurfaces of the same structure.

The buffer layer 53 may be interposed between the light emitting cellsS1, S2 and the substrate 51. The buffer layer 53 is used to relievelattice mismatch between the substrate 51 and the lower semiconductorlayer 55 formed thereon when the substrate 51 is a growth substrate.

The transparent electrode layer 61 is disposed on each of the lightemitting cells S1, S2. Specifically, a first transparent electrode layer61 is disposed on the first light emitting cell S1, and a secondtransparent electrode layer 61 is disposed on the second light emittingcell S2. The transparent electrode layer 61 may be disposed on an uppersurface of the upper semiconductor layer 59 to be connected to the uppersemiconductor layer 59, and may have a smaller area than that of theupper semiconductor layer 59. In other words, the transparent electrodelayer 61 may be recessed from an edge of the upper semiconductor layer59. Thus, the light emitting diode according to this embodiment mayprevent current crowding at the edge of the transparent electrode layer61 through the sidewalls of the light emitting cells S1, S2.

The current blocking layer 60 a may be disposed on each of the lightemitting cells S1, S2 between the transparent electrode layer 61 andeach of the light emitting cells S1, S2. A portion of the transparentelectrode layer 61 is disposed on the current blocking layer 60 a. Thecurrent blocking layer 60 a may be disposed near an edge of each of thelight emitting cells S1, S2, without being limited thereto.Alternatively, the current blocking layer 60 a may be disposed at acentral region of each of the light emitting cells S1, S2. The currentblocking layer 60 a is formed of an insulation material, andparticularly, may include a distributed Bragg reflector formed byalternately stacking layers having different indices of refraction.

The insulation layer 60 b covers a portion of the side surface of thefirst light emitting cell S1. As shown in FIG. 17 and FIG. 18, theinsulation layer 60 b may extend to an area between the first lightemitting cell S1 and the second light emitting cell S2, and may cover aportion of the side surface of the lower semiconductor layer 55 of thesecond light emitting cell S2. The insulation layer 60 b has the samestructure as that of the current blocking layer 60 a and is formed ofthe same material as that of the current blocking layer 60 a, and mayinclude a distributed Bragg reflector. The insulation layer 60 b may beformed of a different process than that of the current blocking layer 60a. When the insulation layer 60 b includes the distributed Braggreflector formed of multiple layers, it is possible to efficientlysuppress formation of defects such as pinholes in the insulation layer60 b. The insulation layer 60 b may be directly connected to the currentblocking layer 60 a to be positioned adjacent thereto, but is notlimited thereto. The insulation layer 60 b may be separated from thecurrent blocking layer 60 a.

The interconnection 65 electrically connects the first light emittingcell S1 to the second light emitting cell S2. The interconnection 65includes a first connection section 65 p and a second connection section65 n. The first connection section 65 p is electrically connected to thetransparent electrode layer 61 on the first light emitting cell S1, andthe second connection section 65 n is electrically connected to thelower semiconductor layer 55 of the second light emitting cell S2. Thefirst connection section 65 p may be disposed near one edge of the firstlight emitting cell S1, without being limited thereto. Alternatively,the first connection section 65 p may be disposed at the central regionof the first light emitting cell S1.

The second connection section 65 n may contact an inclined side surfaceof the second light emitting cell S2, particularly, an inclined sidesurface of the lower semiconductor layer 55 of the second light emittingcell S2. In addition, as shown in FIG. 17, the second connection section65 n may extend in opposite directions along the periphery of the secondlight emitting cell S2 while electrically contacting the inclined sidesurface of the lower semiconductor layer 55. The first light emittingcell S1 is connected in series to the second light emitting cell S2 bythe first and second connection sections 65 p, 65 n of theinterconnection 65.

The interconnection 65 may contact the transparent electrode layer 61over an entire overlapping area between the interconnection 65 and thetransparent electrode layer 61. In the related art, a portion of theinsulation layer 33 may be disposed between the transparent electrodelayer 31 and the interconnection 35. However, in the present exemplaryembodiment, the interconnection 65 directly contacts the transparentelectrode layer 61 without any insulating material interposedtherebetween.

Further, the current blocking layer 60 a may be disposed over the entireoverlapping area between the interconnection 65 and the transparentelectrode layer 61, and the current blocking layer 60 a and theinsulation layer 60 b may be disposed over an entire overlapping areabetween the interconnection 65 and the first light emitting cell S1. Inaddition, the insulation layer 60 b may be disposed between the secondlight emitting cell S2 and the interconnection 65 except for aconnection area between the interconnection 65 and the second lightemitting cell S2.

Although the first connection section 65 p and the second connectionsection 65 n of the interconnection 65 are illustrated as beingconnected to each other via two paths in FIG. 17, the first connectionsection 65 p and the second connection section 65 n may be connected toeach other via a single path.

When the current blocking layer 60 a and the insulation layer 60 b havereflective characteristics like distributed Bragg reflectors, thecurrent blocking layer 60 a and the insulation layer 60 b may besubstantially within the same area as that of the interconnection 65 inan area two times or less than that of the interconnection 65. Thecurrent blocking layer 60 a and the insulation layer 60 b preventabsorption of light by the interconnection 65 when light is emitted fromthe active layer 57. However, when the current blocking layer 60 a andthe insulation layer 60 b occupy an excessively large area, there is apossibility of blocking discharge of light. Thus, it may be necessary tolimit the area of the current blocking layer 60 a and the insulationlayer 60 b.

The insulation protective layer 63 may be disposed outside the area ofthe interconnection 65. The insulation protective layer 63 covers thefirst and second light emitting cells S1, S2 outside the area of theinterconnection 65. The insulation protective layer 63 may be formed ofa silicon oxide layer (SiO₂) or a silicon nitride layer. The insulationprotective layer 63 is formed with an opening through which thetransparent electrode layer 61 on the first light emitting cell S1 andthe lower semiconductor layer of the second light emitting cell S2 areexposed, and the interconnection 65 may be disposed within this opening

A side surface of the insulation protective layer 63 and a side surfaceof the interconnection 65 may be disposed to face each other, or tocontact each other. Alternatively, the side surface of the insulationprotective layer 63 may be separated from the side surface of theinterconnection 65 to face each other.

According to this embodiment, since the second connection section 65 nof the interconnection 65 electrically contacts the inclined sidesurface of the second light emitting cell S2, there is no need forexposure of an upper surface of the lower semiconductor layer 55 of thesecond light emitting cell S2. Thus, there is no need for partialremoval of the second semiconductor layer 59 and the active layer 57,thereby increasing an effective light emitting area of the lightemitting diode.

In addition, the current blocking layer 60 a and the insulation layer 60b may be formed of the same material and have the same structure, andthus may be formed by the same process. Further, since theinterconnection 65 is disposed within the opening of the insulationprotective layer 63, the insulation protective layer 63 and theinterconnection 65 may be formed using the same mask pattern.

In this embodiment, the light emitting diode is illustrated as includingtwo light emitting cells, that is, the first light emitting cell S1 andthe second light emitting cell S2. However, the present invention is notlimited to the two light emitting cells, and more light emitting cellsmay be electrically connected to each other by interconnections 65. Forexample, the interconnections 65 may electrically connect the lowersemiconductor layers 55 of adjacent light emitting cells to thetransparent electrode layers 61 thereof to form a series array of thelight emitting cells. The light emitting diode according to thisembodiment may include a plurality of such arrays, which is connected toeach other in reverse parallel and connected to an AC source. Inaddition, the light emitting diode may be provided with a bridgerectifier (not shown) connected to the series array of light emittingcells, such that the light emitting cells can be driven by an AC source.The bridge rectifier may be formed by connecting the light emittingcells having the same structure as that of the light emitting cells S1,S2 using the interconnections 65.

FIG. 19 to FIG. 25 are sectional views illustrating a method offabricating a light emitting diode according to one embodiment of theinvention.

Referring to FIG. 19, a semiconductor stack structure 56 is formed on asubstrate 51, and includes a lower semiconductor layer 55, an activelayer 57 and an upper semiconductor layer 59. In addition, beforeformation of the lower semiconductor layer 55, a buffer layer 53 may beformed on the substrate 51.

The substrate 51 may be a sapphire (Al₂O₃) substrate, a silicon carbide(SiC) substrate, a zinc oxide (ZnO) substrate, a silicon (Si) substrate,a gallium arsenide (GaAs), a gallium phosphide (GaP) substrate, alithium alumina (LiAl₂O₃) substrate, a boron nitride (BN) substrate, analuminum nitride (AlN) substrate, or a gallium nitride (GaN) substrate,without being limited thereto. That is, the substrate 51 may be selectedfrom among various materials dependent upon materials of semiconductorlayers to be formed thereon. In addition, the substrate 51 may be asubstrate having a convex-concave pattern (not shown) on an uppersurface thereof, such as a patterned sapphire substrate.

The buffer layer 53 is formed to relieve lattice mismatch between thesubstrate 51 and the semiconductor layer 55 formed thereon, and may beformed of, for example, gallium nitride (GaN) or aluminum nitride (AlN).When the substrate 51 is a conductive substrate, the buffer layer 53 maybe formed as an insulation layer or a semi-insulation layer, forexample, AlN or semi-insulation GaN.

Each of the lower semiconductor layer 55, the active layer 57 and theupper semiconductor layer 59 may be formed of a gallium nitride-basedsemiconductor material, for example, (Al, In, Ga)N. The lower and uppersemiconductor layers 55, 59 and the active layer 57 may bediscontinuously or continuously formed by metal organic chemical vapordeposition (MOCVD), molecular beam epitaxy, hydride vapor phase epitaxy(HVPE), and the like.

Here, the lower and upper semiconductor layers are n-type and p-typesemiconductor layers, respectively, or vice versa. The n-typesemiconductor layer is formed by doping a gallium nitride-based compoundsemiconductor layer with, for example, silicon (Si) impurities, and thep-type semiconductor layer is formed by doping the gallium nitride-basedcompound semiconductor layer with, for example, magnesium (Mg)impurities.

Referring to FIG. 20, a plurality of light emitting cells S1, S2 isformed to be separated from each other by photolithography and etching.Each of the light emitting cells S1, S2 has an inclined side surface. Ina conventional method of fabricating a light emitting diode,photolithography and etching processes are added to expose a portion ofan upper surface of the lower semiconductor layer 55 of each of thelight emitting cells S1, S2. In this embodiment, however, thephotolithography and etching processes for partially exposing the uppersurface of the lower semiconductor layer 55 are omitted.

Referring to FIG. 21, a current blocking layer 60 a covering a partialarea of the first light emitting cell S1 is formed together with aninsulation layer 60 b covering a partial area of a side surface of thefirst light emitting cell S1. The insulation layer 60 b may also extendto cover an area between the first light emitting cell S1 and the secondlight emitting cell S2, and may cover a portion of the side surface ofthe lower semiconductor layer 55 of the second light emitting cell S2.

The current blocking layer 60 a and the insulation layer 60 b may beformed by depositing an insulation material layer, followed bypatterning the insulation material layer through photolithography andetching. Alternatively, the current blocking layer 60 a and theinsulation layer 60 b may be formed as insulation material layersthrough a lift-off process. In particular, the current blocking layer 60a and the insulation layer 60 b may be formed as distributed Braggreflectors by alternately stacking layers having different indices ofrefraction, for example, a SiO₂ layer and a TiO₂ layer. When theinsulation layer 60 b is a distributed Bragg reflector formed ofmultiple layers, it is possible to prevent formation of defects such aspinholes in the insulation layer 60 b, whereby the insulation layer 60 bmay be formed to be relatively thin as compared with conventionaltechniques.

As shown in FIG. 21, the current blocking layer 60 a and the insulationlayer 60 b may be connected to each other, without being limitedthereto.

Next, a transparent electrode layer 61 is formed on the first and secondlight emitting cells S1, S2. The transparent electrode layer 61 may beformed of a conductive material such as indium tin oxide (ITO) or zincoxide, or a metal layer such as Ni/Au. The transparent electrode layer61 is connected to the upper semiconductor layer 59 and is partiallydisposed on the current blocking layer 60 a. The transparent electrodelayer 61 may be formed by a lift-off process, without being limitedthereto. Alternatively, the transparent electrode layer 61 may be formedby photolithography and etching.

Referring to FIG. 22, an insulation protective layer 63 is formed tocover the first and second light emitting cells S1, S2. The insulationprotective layer 63 covers the transparent electrode layer 61 and theinsulation layer 60 b. In addition, the insulation protective layer 63may cover an overall area of the first and second light emitting cellsS1, S2. The insulation protective layer 63 may be formed as aninsulation material layer such as a silicon oxide layer or a siliconnitride layer by chemical vapor deposition or the like.

Referring to FIG. 23, a mask pattern 70 having an opening is formed onthe insulation protective layer 63. The opening of the mask pattern 70corresponds to an area of the interconnection. Next, some region of theinsulation protective layer 63 is etched using the mask pattern 70 as amask. As a result, an opening is formed in the insulation protectivelayer 63 to expose some of the transparent electrode layer 61 and theinsulation layer 60 b, and an inclined side surface of the lowersemiconductor layer 55 of the second light emitting cell S2therethrough.

Referring to FIG. 24, with the mask pattern 70 remaining on theinsulation protective layer 63, a conductive material is deposited toform an interconnection 65 in the opening of the mask pattern 70. Atthis point, a portion 65 a of the conductive material may be depositedon the mask pattern 70. The conductive material may be deposited byplating, electron-beam evaporation or sputtering.

Referring to FIG. 25, the mask pattern 70 is removed together with theportion 65 a of the conductive material on the mask pattern 70.Accordingly, the interconnection 65 electrically connecting the firstand second light emitting cells S1, S2 to each other is finally formed.

Here, a first connection section 65 p of the interconnection 65 isconnected to the transparent electrode layer 61 of the first lightemitting cell S1, and a second connection section 65 n of theinterconnection 65 is connected to the inclined side surface of thelower semiconductor layer 55 of the second light emitting cell S2. Thefirst connection section 65 p of the interconnection 65 is connected tothe transparent electrode layer 60 a within an upper area of the currentblocking layer 60 a. The interconnection 65 is separated from the sidesurface of the first light emitting cell S1 by the insulation layer 60b.

In this embodiment, the current blocking layer 60 a and the insulationlayer 60 b are formed by the same process. Accordingly, the insulationprotective layer 63 and the interconnection 65 may be formed using thesame mask pattern 70, whereby the light emitting diode can be fabricatedusing the same number of exposure processes while adding the currentblocking layer 60 a.

FIG. 26 is a schematic sectional view of a light emitting diodeaccording to an exemplary embodiment of the present invention.

Referring to FIG. 26, the light emitting diode according to the presentexemplary embodiment is generally similar to the light emitting devicedescribed with reference to FIG. 17 and FIG. 18, and further includes atransparent conductive layer 62.

In the light emitting diode according to this embodiment, a substrate51, light emitting cells S1, S2, a buffer layer 53, a transparentelectrode layer 61, a current blocking layer 60 a, an insulation layer60 b, an insulation protective layer 63 and an interconnection 65 aresimilar to those of the light emitting diode according to the aboveembodiment described with reference to FIG. 17 and FIG. 18, and detaileddescriptions thereof will be omitted.

The transparent conductive layer 62 is disposed between the insulationlayer 60 b and the interconnection 65. The transparent conductive layer62 has a narrower line width than the insulation layer 60 b, therebypreventing short circuit of the upper semiconductor layer 59 and thelower semiconductor layer 55 due to the transparent conductive layer 62.

On the other hand, the transparent conductive layer 62 is connected tothe first transparent electrode layer 61, and may connect the firsttransparent electrode layer 61 to the second light emitting cell S2. Forexample, one end of the transparent conductive layer 62 may beelectrically connected to the lower semiconductor layer 55 of the secondlight emitting cell. In addition, when two or more light emitting cellsare connected to each other, a second transparent conductive layer 62may extend from a second transparent electrode layer 61 on the secondlight emitting cell S2.

In this embodiment, since the transparent conductive layer 62 isdisposed between the interconnection 65 and the insulation layer 60 b,electric current can flow through the transparent conductive layer 62even in the case where the interconnection 65 is disconnected, therebyimproving electric stability of the light emitting diode.

FIG. 27 to FIG. 30 are schematic sectional views illustrating a methodof fabricating a light emitting diode according to the exemplaryembodiment of FIG. 26.

Referring to FIG. 27, as in the method described with reference to FIG.19 and FIG. 20, a semiconductor stack structure 56 is formed on asubstrate 51 and a plurality of light emitting cells S1, S2 is formed tobe separated from each other via photolithography and etching. Then, asdescribed with reference to FIG. 21, a current blocking layer 60 acovering a partial area of the first light emitting cell S1 is formedtogether with an insulation layer 60 b covering a partial area of a sidesurface of the first light emitting cell S1.

As described with reference to FIG. 21, the current blocking layer 60 aand the insulation layer 60 b may be formed as distributed Braggreflectors by alternately stacking layers having different indices ofrefraction, for example, a SiO₂ layer and a TiO₂ layer. When theinsulation layer 60 b is a distributed Bragg reflector formed ofmultiple layers, it is possible to prevent formation of defects such aspinholes in the insulation layer 60 b, whereby the insulation layer 60 bmay be formed to be relatively thin as compared with conventionaltechniques.

Next, a transparent electrode layer 61 is formed on the first and secondlight emitting cells S1, S2. As described with reference to FIG. 21, thetransparent electrode layer 61 may be formed of a conductive materialsuch as indium tin oxide (ITO) or zinc oxide, or a metal layer such asNi/Au. The transparent electrode layer 61 is connected to the uppersemiconductor layer 59 and is partially disposed on the current blockinglayer 60 a. The transparent electrode layer 61 may be formed by alift-off process, without being limited thereto. Alternatively, thetransparent electrode layer 61 may be formed by photolithography andetching.

During formation of the transparent electrode layer 61, a transparentconductive layer 62 is also formed. The transparent conductive layer 62may be formed of the same material as that of the transparent electrodelayer 61 through the same process. The transparent conductive layer 62is formed on the insulation layer 60 b, and may be connected to thetransparent electrode layer 61. Further, one end of the transparentconductive layer 62 may be electrically connected to an inclined sidesurface of the lower semiconductor layer 55 of the second light emittingcell S2.

Referring to FIG. 28, an insulation protective layer 63 is formed tocover the first and second light emitting cells S1, S2. The insulationprotective layer 63 covers the transparent electrode layer 61, thetransparent conductive layer 62 and the insulation layer 60 b. Inaddition, the insulation protective layer 63 may cover an overall areaof the first and second light emitting cells S1, S2. The insulationprotective layer 63 may be formed as an insulation material layer suchas a silicon oxide layer or a silicon nitride layer by chemical vapordeposition or the like.

Referring to FIG. 29, as described with reference to FIG. 23, a maskpattern 70 having an opening is formed on the insulation protectivelayer 63. The opening of the mask pattern 70 corresponds to an area ofthe interconnection. Next, some region of the insulation protectivelayer 63 is etched using the mask pattern 70 as a mask. As a result, anopening is formed in the insulation protective layer 63 to expose someof the transparent electrode layer 61 and the transparent conductivelayer 62, and the inclined side surface of the lower semiconductor layer55 of the second light emitting cell S2 therethrough. A portion of theinsulation layer 60 b is exposed through the opening. Further, a portionof the insulation layer 60 b is exposed through the opening.

Referring to FIG. 30, as described with reference to FIG. 24, with themask pattern 70 remaining on the insulation protective layer 63, aconductive material is deposited to form an interconnection 65 in theopening of the mask pattern 70.

Next, as described with reference to FIG. 25, the mask pattern 70 isremoved together with a portion 65 a of the conductive material on themask pattern 70. Accordingly, the interconnection 65 electricallyconnecting the first and second light emitting cells S1, S2 to eachother is finally formed.

In the embodiment described with reference to FIG. 19 to FIG. 25, theinsulation layer 60 b may be damaged during etching of the insulationprotective layer 63. For example, when the insulation protective layer63 is subjected to etching using an etching solution such as fluoricacid, the insulation layer 60 b including an oxide layer may be damagedby the etching solution. Thus, the insulation layer 60 b may notinsulate the interconnection 65 from the first light emitting cell S1,thereby causing short circuit.

In the present exemplary embodiment, since the transparent conductivelayer 62 is disposed on the insulation layer 60 b, the insulation layer60 b under the transparent conductive layer 62 can be protected frometching damage. Thus, it is possible to prevent short circuit due to theinterconnection 65.

In this embodiment, the transparent electrode layer 61 and thetransparent conductive layer 62 may be formed by the same process. Thus,the light emitting diode can be fabricated using the same number ofexposure processes while adding the transparent conductive layer 62.

FIG. 31 is a schematic plan view of a light emitting diode according toan exemplary embodiment of the present invention, and FIG. 32 is aschematic sectional view taken along line B-B of FIG. 31.

Referring to FIG. 31 and FIG. 32, the light emitting diode includes asubstrate 151, light emitting cells S1, S2, a first insulation layer 160a, a second insulation layer 160 b, a transparent electrode layer 161,and an interconnection 165. The light emitting diode may further includea buffer layer 153.

The substrate 151 may be an insulating or conductive substrate. Forexample, the substrate 151 may be a sapphire substrate, a galliumnitride substrate, a silicon carbide (SiC) substrate, or a siliconsubstrate. In addition, the substrate 151 may be a substrate having aconvex-concave pattern (not shown) on an upper surface thereof, such asa patterned sapphire substrate.

On a single substrate 151, the first light emitting cell S1 and thesecond light emitting cell S2 are separated from each other. The firstand second light emitting cells S1, S2 may be composed of a galliumnitride semiconductor. Each of the first and second light emitting cellsS1, S2 has a stack structure 156, which includes a lower semiconductorlayer 155, an upper semiconductor layer 159 disposed on one area of thelower semiconductor layer, and an active layer 157 interposed betweenthe lower semiconductor layer and the upper semiconductor layer. Here,the lower and lower semiconductor layers 155, 159 may be p-type andn-type semiconductor layers, respectively, or vice versa.

Each of the lower semiconductor layer 155, the active layer 157 and theupper semiconductor layer 159 may be formed of a gallium nitride-basedmaterial, for example, (Al, In, Ga)N. The active layer 157 may be formedof a material having a composition capable of emitting light in adesired wavelength range, for example, UV or blue light, and the lowerand upper semiconductor layers 155, 159 are formed of a material havinga wider band gap than that of the active layer 157.

As shown, the lower semiconductor layer 155 and/or the uppersemiconductor layer 159 may be formed of a single layer or multiplelayers. In addition, the active layer 157 may have a single quantum-wellstructure or a multi-quantum well structure.

Each of the first and second light emitting cells S1, S2 may have aninclined side surface, an inclined angle of which ranges from 15° to 80°with respect to an upper surface of the substrate 151.

The active layer 157 and the upper semiconductor layer 159 may be placedon some region of the lower semiconductor layer 155, and the otherregion of the lower semiconductor layer 155 may be exposed, as shown inFIG. 32. Alternatively, an upper surface of the lower semiconductorlayer 155 may be completely covered by the active layer 157 such that aside surface of the lower semiconductor layer 155 is exposed.

In FIG. 32, the first light emitting cell S1 and the second lightemitting cell S2 are partially shown. However, it should be noted thatthe first light emitting cell S1 and the second light emitting cell S2may have a similar or the same structure, as shown in FIG. 31.Specifically, the first and second light emitting cells S1, S2 may havethe same gallium nitride-based semiconductor stack structure, and mayhave inclined side surfaces of the same structure.

The buffer layer 153 may be interposed between the light emitting cellsS1, S2 and the substrate 151. The buffer layer 153 is used to relievelattice mismatch between the substrate 151 and the lower semiconductorlayer 155 formed thereon, when the substrate 151 is a growth substrate.

The transparent electrode layer 161 is disposed on each of the lightemitting cells S1, S2. Specifically, a first transparent electrode layer161 is disposed on the first light emitting cell S1, and a secondtransparent electrode layer 161 is disposed on the second light emittingcell S2. The transparent electrode layer 161 may be disposed on an uppersurface of the upper semiconductor layer 159 to be connected to theupper semiconductor layer 159.

The first and/or the second transparent electrode layers 161 may cover aportion of the side surfaces of the first and/or second light emittingcells S1, S2, and may cover at least three surfaces thereof. In theembodiment shown in FIG. 31, each of the first and second transparentelectrode layers 161 covers four side surfaces of the first or secondlight emitting cell S1 or S2.

Accordingly, the transparent electrode layer 161 may have a wider areathan an upper area of the corresponding light emitting cell S1 or S2. Inaddition, the transparent electrode layer 161 may cover the entirety ofthe upper surface of the upper semiconductor layer 159. The transparentelectrode layer 161 has a wider area than that of the correspondinglight emitting cell S1 or S2, whereby resistance of the transparentelectrode layer 161 can be reduced. The transparent electrode layer 161placed on the second light emitting cell S2 adjoins the uppersemiconductor layer 159 of the second light emitting cell S2 and isinsulated from the lower semiconductor layer 155 of the second lightemitting cell S2 by the first insulation layer 160 a. Namely, thetransparent electrode layer 161 may adjoin an exposed region of theupper semiconductor layer 159 and may be placed on the first insulationlayer 160 a covering an exposed region of the lower semiconductor layer155.

The first insulation layer 160 a separates the transparent electrodelayer 161 from the side surface of the corresponding light emitting cellS1 or S2 to prevent the light emitting cell S1 or S2 from beingelectrically disconnected from the transparent electrode layer 161. Thefirst insulation layer 160 a may cover the side surface of thecorresponding light emitting cell S1 or S2 along an edge of thecorresponding light emitting cell. In addition, the first insulationlayer 160 a may cover the upper surface of the substrate 151 around thelight emitting cells S1, S2. On the other hand, the first insulationlayer 160 a has an opening 160 hn that exposes the lower semiconductorlayer 155 and an opening 160 hp that exposes the upper semiconductorlayer 159. The transparent electrode layer 161 is connected to the uppersemiconductor layer 159 through the opening 160 hp formed on an uppersurface of each of the light emitting cells S1, S2. As the firstinsulation layer 160 a is formed along an edge of the upper surface ofthe upper semiconductor layer 159, the transparent electrode layer 161may be recessed from the edge of the upper semiconductor layer 159 to beconnected to the upper semiconductor layer 159. Thus, the light emittingdiode according to this embodiment can prevent current crowding at theedge of the upper semiconductor layer 159 through sidewalls of the lightemitting cells S1, S2.

The second insulation layer 160 b may be formed on each of the lightemitting cells S1, S2 to be placed between the transparent electrodelayer 161 and the light emitting cells S1, S2. A portion of thetransparent electrode layer 161 is placed on the second insulation layer160 b. The second insulation layer 160 b may be disposed near an edge ofeach of the light emitting cells S1, S2, without being limited thereto.Alternatively, the second insulation layer 160 b may be disposed at acentral region of each of the light emitting cells S1, S2. The secondinsulation layer 160 b may be formed of the same material, for example,silicon oxide or silicon nitride, as that of the first insulation layer160 a.

The interconnection 165 electrically connects the first light emittingcell S1 to the second light emitting cell S2. The interconnection 165includes a first connection section (one end) 165 p and a secondconnection section (the other end) 165 n. The first connection section165 p is electrically connected to the transparent electrode layer 161on the first light emitting cell S1, and the second connection section165 n is electrically connected to the lower semiconductor layer 155 ofthe second light emitting cell S2. Particularly, the second connectionsection 165 n may be connected to the lower semiconductor layer 155through the opening 160 hn of the first insulation layer 160 a. Thefirst light emitting cell S1 is connected in series to the second lightemitting cell S2 through the first and second connection sections 165 p,65 n of the interconnection 165.

On the other hand, the first connection section 165 p may be disposednear one edge of the first light emitting cell S1, without being limitedthereto. Alternatively, the first connection section 165 p may bedisposed at the central region of the first light emitting cell S1.

The interconnection 165 may contact the transparent electrode layer 161over an entire overlapping area between the interconnection 165 and thetransparent electrode layer 161. In the related art, a portion of theinsulation layer 133 is disposed between the transparent electrode layer131 and the interconnection 135. However, in this embodiment, theinterconnection 165 directly contacts the transparent electrode layer161 without any insulating material interposed therebetween.

Further, the second insulation layer 160 a may be disposed over theentire overlapping area between the interconnection 165 and thetransparent electrode layer 161 on the first light emitting cell S1.

In this embodiment, the second connection section 165 n is connected tothe exposed upper side of the lower semiconductor layer 155.Alternatively, the second connection section 165 n may be connected toan inclined side surface of the second light emitting cell S2,particularly, an inclined side surface of the lower semiconductor layer155 of the second light emitting cell S2. In this case, there is no needfor exposure of the upper surface of the lower semiconductor layer 155,and the first insulation layer 160 a is formed to expose the inclinedside surface of the lower semiconductor layer 155.

In this embodiment, the light emitting diode is illustrated as includingtwo light emitting cells, that is, the first light emitting cell S1 andthe second light emitting cell S2. However, the present invention is notlimited thereto, and more light emitting cells may be electricallyconnected to each other by the interconnections 165. For example, theinterconnections 165 may electrically connect the lower semiconductorlayers 155 of adjacent light emitting cells to the transparent electrodelayers 161 thereof to form a series array of light emitting cells.Although the light emitting diode may have a single series array formedon a single substrate 151, the present invention is not limited thereto.Alternatively, the light emitting diode may include a plurality ofseries arrays, which are connected to each other in parallel or inreverse parallel. In addition, the light emitting diode may be providedwith a bridge rectifier (not shown) connected to the series array oflight emitting cells, such that the light emitting cells can be drivenby an AC source. The bridge rectifier may be formed by connecting thelight emitting cells having the same structure as that of the lightemitting cells S1, S2 using the interconnections 165.

FIG. 33 to FIG. 37 are sectional views illustrating a method offabricating a light emitting diode according to the exemplary embodimentof FIG. 31.

Referring to FIG. 33, a semiconductor stack structure 156 is formed on asubstrate 151, and includes a lower semiconductor layer 155, an activelayer 157 and an upper semiconductor layer 159. In addition, beforeformation of the lower semiconductor layer 155, a buffer layer 153 maybe formed on the substrate 151.

The substrate 151 may be a sapphire (Al₂O₃) substrate, a silicon carbide(SiC) substrate, a zinc oxide (ZnO) substrate, a silicon (Si) substrate,a gallium arsenide (GaAs), a gallium phosphide (GaP) substrate, alithium alumina (LiAl₂O₃) substrate, a boron nitride (BN) substrate, analuminum nitride (AlN) substrate, or a gallium nitride (GaN) substrate,without being limited thereto. That is, the substrate 151 may be formedof a material selected from among various materials dependent uponmaterials of semiconductor layers to be formed thereon. In addition, thesubstrate 151 may be a substrate having a convex-concave pattern on anupper surface thereof, such as a patterned sapphire substrate.

The buffer layer 153 is formed to relieve lattice mismatch between thesubstrate 151 and the semiconductor layer 155 formed thereon, and may beformed of, for example, gallium nitride (GaN) or aluminum nitride (AlN).When the substrate 51 is a conductive substrate, the buffer layer 153may be formed as an insulation layer or a semi-insulation layer, forexample, AlN or semi-insulation GaN.

Each of the lower semiconductor layer 155, the active layer 157 and theupper semiconductor layer 159 may be formed of a gallium nitride-basedsemiconductor material, for example, (Al, In, Ga)N. The lower and uppersemiconductor layers 155, 159 and the active layer 157 may bediscontinuously or continuously formed by metal organic chemical vapordeposition (MOCVD), molecular beam epitaxy, hydride vapor phase epitaxy(HVPE), and the like.

Here, the lower and upper semiconductor layers may be n-type and p-typesemiconductor layers, respectively, or vice versa. The n-typesemiconductor layer may be formed by doping a gallium nitride-basedcompound semiconductor layer with, for example, silicon (Si) impurities,and the p-type semiconductor layer may be formed by doping the galliumnitride-based compound semiconductor layer with, for example, magnesium(Mg) impurities.

Referring to FIG. 34, a plurality of light emitting cells S1, S2 isformed to be separated from each other by photolithography and etching.Each of the light emitting cells S1, S2 may be formed to have aninclined side surface, and an upper surface of the lower semiconductorlayer 155 of each of the light emitting cells S1, S2 is partiallyexposed.

In each of the light emitting cells S1, S2, the lower semiconductorlayer 155 is first exposed by mesa-etching, and the light emitting cellsare separated from each other by a cell isolation process.Alternatively, the light emitting cells S1, S2 may be first separatedfrom each other by the cell isolation process, and then are subjected tomesa etching to expose the lower semiconductor layers 155 thereof.

When an interconnection is connected to an inclined side surface, mesaetching for exposing the upper surface of the lower semiconductor layer155 may be omitted.

Referring to FIG. 35, a second insulation layer 160 b covering someregion of the first light emitting cell S1 is formed together with afirst insulation layer 160 b covering a side surface of the first lightemitting cell S1. The first insulation layer 160 a may extend to cover aregion between the first light emitting cell S1 and the second lightemitting cell S2. The first insulation layer 160 a has an opening 160 hpexposing the upper semiconductor layer 159 and an opening 160 hnexposing the lower semiconductor layer 155. On the other hand, the firstinsulation layer 160 a may be connected to the second insulation layer160 b, but the present invention is not limited thereto. In someembodiments, the first insulation layer 160 a may be separated from thesecond insulation layer 160 b.

The first insulation layer 160 a and the second insulation layer 160 bmay be formed of silicon oxide or silicon nitride by the same process atthe same time. For example, the first and second insulation layers 160a, 160 b may be formed by depositing an insulating material, followed bypatterning through photolithography and etching.

Next, referring to FIG. 36, a transparent electrode layer 161 is formedon the first and second light emitting cells S1, S2. The transparentelectrode layer 161 is formed of a conductive oxide such as indium tinoxide (ITO) or zinc oxide, or a metal layer such as Ni/Au. Thetransparent electrode layer 161 is connected to the upper semiconductorlayer 159 through the opening 160 hp and covers the second insulationlayer 160 b.

In addition, the transparent electrode layer 161 covers side surfaces ofthe light emitting cells S1, S2. The transparent electrode layer 161 mayalso cover at least three side surfaces of the corresponding lightemitting cell S1 or S2. Here, the transparent electrode layer 161 isformed outside the opening 160 hn such that the lower semiconductorlayer 153 is exposed.

On the other hand, the transparent electrode layer 161 is separated fromthe side surface of the light emitting cell S1 or S2 by the firstinsulation layer 161 a. In addition, a first transparent electrode layer161 on the first light emitting cell S1 is separated from a secondtransparent electrode layer 161 on the second light emitting cell S2,and may be separated from the second light emitting cell S2.

The transparent electrode layer 161 may be formed by a lift-off process,without being limited thereto. Alternatively, the transparent electrodelayer 161 may be formed by photolithography and etching.

Referring to FIG. 37, an interconnection 165 is formed on thetransparent electrode layer 161. The interconnection 165 includes afirst connection section 165 p and a second connection section 165 n, inwhich the first connection section 165 p is connected to the firsttransparent electrode layer 161 of the first light emitting cell S1 andthe second connection section 165 n is connected to the lowersemiconductor layer 155 of the second light emitting cell S2. Theinterconnection 165 may be formed by a lift-off process.

According to this embodiment, the first insulation layer 160 a and thesecond insulation layer 160 b may be formed at the same time, therebysimplifying the fabrication process. Furthermore, the method accordingto this embodiment does not include an etching process using BOE afterformation of the first and second insulation layers 160 a, 160 b,thereby preventing damage to the first and second insulation layers 160a, 160 b in a subsequent process using BOE or the like.

FIG. 38 is a sectional view of a light emitting diode according toanother exemplary embodiment of the present invention, and FIG. 39 is asectional view taken along line B-B of FIG. 38.

Referring to FIG. 38 and FIG. 39, the light emitting diode according tothis embodiment is generally similar to the light emitting diodeillustrated with reference to FIG. 31 and FIG. 32 excluding a locationof the transparent electrode layer 161.

Namely, in the embodiment shown in FIG. 31 and FIG. 32, the transparentelectrode layer 161 is formed to cover four side surfaces of thecorresponding light emitting cell S1 or S2, and is separated from anadjacent light emitting cell. On the contrary, in this embodiment, thefirst transparent electrode layer 161 covers three side surfaces of thefirst light emitting cell S1 while extending to cover a portion of theside surface of the second light emitting cell S2.

The first transparent electrode layer 161 may be connected to the lowersemiconductor layer 155 of the second light emitting cell S2. However,the first transparent electrode layer 161 is separated from the secondtransparent electrode layer and is also separated from the uppersemiconductor layer 159 of the second light emitting cell S2.

According to this embodiment, current can be supplied between adjacentlight emitting cells S1, S2 using the transparent electrode layer 161,thereby further reducing forward voltage of the light emitting diode.

A description of a method fabricating the light emitting diode accordingto this embodiment of the invention will be omitted to avoid repetition.

Although various embodiments have been described above, the presentinvention is not limited thereto, and various modification, changes, andalterations can be made without departing from the scope of the presentinvention.

FIG. 40 is a schematic plan view of a light emitting diode according toan exemplary embodiment of the present invention, FIG. 41 a and FIG. 41b are sectional views taken along lines A-A and B-B of FIG. 40, and FIG.42 is a schematic circuit diagram of the light emitting diode of FIG.40.

Referring to FIG. 40 to FIG. 42, the light emitting diode includes asubstrate 221, a plurality of light emitting cells LEC, a currentblocking layer 229, a transparent electrode layer 231, an insulationprotective layer 233, first interconnections 235, secondinterconnections 237, a first electrode pad 239 a, and a secondelectrode pad 239 b.

The substrate 221 serves to support the light emitting cells LEC, andmay be a growth substrate for growing a nitride semiconductor layer,such as a sapphire substrate, a silicon substrate, and a GaN substrate,without being limited thereto. The substrate 221 typically means asubstrate in a light emitting diode chip.

The plural light emitting cells LEC are arranged on the substrate 221.As shown in FIG. 41 a and FIG. 41 b, each of the light emitting cellsLEC includes a first conductive type semiconductor layer 223, an activelayer 225, and a second conductive type semiconductor layer 227. Herein,the first and second conductive type semiconductor layers 223, 227 maybe n-type and p-type semiconductor layers, respectively, or vice versa.The active layer 225 is placed between the first conductive typesemiconductor layer 223 and the second conductive type semiconductorlayer 227, and may have a single quantum well structure or amulti-quantum well structure. A material and composition of the activelayer 225 are determined dependent on a desired wavelength of light. Forexample, the active layer 225 may be formed of an AlInGaN-based compoundsemiconductor, for example, InGaN. The first and second conductive typesemiconductor layers 223, 227 are composed of an AlInGaN-based compoundsemiconductor, which has a wider band gap than that of the active layer225, for example, GaN. On the other hand, a buffer layer (not shown) maybe interposed between the first conductive type semiconductor layer 223and the substrate 221.

The first conductive type semiconductor layer 223, active layer 225 andsecond conductive type semiconductor layer 227 may be grown on thesubstrate 221 by metal organic chemical vapor deposition, followed bypatterning through photolithography and etching.

As shown in FIG. 40 and FIG. 41 a, the active layer 225 and the secondconductive type semiconductor layer 227 may be divided from each otheron a single first conductive type semiconductor layer 223. That is, twolight emitting cells LEC may share the first conductive typesemiconductor layer 223.

The interconnections, that is, the first interconnections 235 and thesecond interconnections 237, electrically connect the light emittingcells LEC to each other. The first and second interconnections 235connect the light emitting cells LEC placed on different firstconductive type semiconductor layers 223 to each other in series. Thefirst interconnections 235 electrically connect the first conductivetype semiconductor layer 223 of one light emitting cell to the secondconductive type semiconductor layer 227 of an adjacent light emittingcell LEC.

The first interconnection 235 includes a first connection section 235 a(an anode) connected to the first conductive type semiconductor layer223, a second connection section 235 b (a cathode) placed on the secondconductive type semiconductor layer 227 to be electrically connected tothe second conductive type semiconductor layer 227, and aninterconnecting section 235 c interconnecting the first connectionsection 235 a and the second connection section 235 b.

The second interconnection 237 includes a first connection section 237 a(a common anode) connected to the first conductive type semiconductorlayer 223, a second connection section 237 b (a common cathode) placedon the second conductive type semiconductor layer 227 to be electricallyconnected to the second conductive type semiconductor layer 227, and aninterconnecting section 237 c interconnecting the first connectionsection 237 a and the second connection section 237 b.

The common anode 237 a is commonly connected to two light emitting cellsLEC. For example, the common anode 237 a is electrically connected to,for example, the first conductive type semiconductor layer shared by thetwo light emitting cells LEC. On the other hand, the common cathode 237b is commonly connected to the two light emitting cells 2LEC. Forexample, the common cathode 237 b is electrically connected to thesecond conductive type semiconductor layers 227 placed on the sharedfirst conductive type semiconductor layer 223. The common cathode 237 bis placed on a region between the two light emitting cells 2LEC.

Although the first and second interconnections 235, 237 have beendescribed above, it should be understood that the light emitting cellsLEC may be connected to each other by various types of interconnections.For example, like the interconnections that connect the first lightemitting cell to two light emitting cells adjacent the first lightemitting cell in FIG. 40, the first connection section 235 a connectedto one light emitting cell LEC may be connected to the common cathode237 b commonly connected to two light emitting cells LEC by theinterconnecting section. In addition, the common anode 235 b may beconnected to the two second connection sections 237 b and the two firstconnection sections 235 a may be connected to the common cathode 237 b.

Plural series arrays are formed by the interconnections 235, 237 and areconnected to each other in parallel.

On the other hand, the transparent electrode layers 231 are connected tothe second conductive type semiconductor layers 227 of the lightemitting cells LEC. Although some of the transparent electrode layers231 are restrictively placed on the corresponding light emitting cells,the other transparent electrode layers 231 may be continuously placed onthe two light emitting cells LEC.

The cathodes 235 b, 237 b may be electrically connected to the secondconductive type semiconductor layer 227 through the transparentelectrode layer 231. Particularly, the common cathode 237 b may beelectrically connected to the two light emitting cells LEC at the sametime through the transparent electrode layer 231 continuously placed onthe two light emitting cells.

The current blocking layer 229 is placed below the common cathode 237 b.Particularly, the current blocking layer 229 is placed under thetransparent electrode layer 231 to separate the transparent electrodelayer 231 from side surfaces of the light emitting cells 2LEC,particularly from the first conductive type semiconductor layer 223.Furthermore, the current blocking layer 229 may partially cover upperregions of the light emitting cells LEC. In addition, the currentblocking layer (not shown) may be placed under the cathode 235 b.

The current blocking layer 229 is formed of an insulation layer toprevent current crowding under the cathodes 235 b, 237 b. Furthermore,the current blocking layer 229 may include a distributed Braggreflector. The distributed Bragg reflector, which reflects light emittedfrom the active layer 225, may be formed by repeatedly stacking layershaving difference indexes of refraction, for example, TiO₂/SiO₂. As thecurrent blocking layer 229 includes the distributed Bragg reflector, itis possible to prevent light generated from the active layer 223 frombeing absorbed into the interconnections 235, 237.

As shown in FIG. 40, a portion of the current blocking layer 229 mayextend outside the first conductive type semiconductor layer 223. Aportion of the interconnecting section 237 c may be placed on theextended portion of the current blocking layer 229, and thus, theextended portion will reflect light traveling towards theinterconnecting section 237 c. On the other hand, the transparentelectrode layer 231 may extend to cover the extended portion of thecurrent blocking layer 229. Further, the transparent electrode layer 231may further extend to cover a portion of an adjacent first conductivetype semiconductor layer 223.

The first electrode pad 239 a and the second electrode pad 239 b areplaced at opposite ends of the series arrays. The first and secondelectrode pads 239 a, 239 b may be respectively placed on the lightemitting cells LEC at the opposite sides of the series arrays.

The insulation protective layer 233 may cover substantially the entiretyof the light emitting diode excluding regions at which theinterconnections 235, 237 and the electrode pads 239 a, 239 b will beformed. The insulation protective layer 233 may be formed to protect thelight emitting diode from external moisture or external force.

According to this embodiment, as shown in FIG. 42, two series arrays ofthe light emitting cells LEC may be formed between the first electrodepad 239 a and the second electrode pad 239 b. In FIG. 42, one lightemitting cell is placed at one end of the series arrays at which thesecond electrode pad 239 b is placed, and two light emitting cells areplaced at the other end thereof at which the first electrode pad 239 ais placed. However, the present invention is not limited to thisarrangement of the light emitting cells LEC. For example, one or twolight emitting cells may be placed at either end of these arrays.

In addition, according to this embodiment, as indicated by a dotted linein FIG. 42, the common cathode 237 a or the interconnection 237including the common cathode 237 a is provided to interconnect arrays,which are connected to each other in parallel. As a result, the lightemitting cells connected to the common cathode have equivalentpotential, thereby relieving current crowding on a certain array.

Although this embodiment has been illustrated as having four lightemitting cells in a series array, the number of light emitting cells inthe series array is not particularly limited so long as the series arrayincludes one or more light emitting cells. In addition, the number oflight emitting cells may be determined in various ways as needed or inconsideration of available voltage.

Further, this embodiment has been illustrated as having aseries-parallel structure in which two series arrays are formed on thesubstrate 221 by the interconnections and connected to each other inparallel. However, it should be understood that the number of seriesarrays formed on the substrate 221 is not limited thereto and moreseries arrays may be formed thereon.

FIG. 43 is a schematic circuit diagram illustrating a light emittingdiode according to a further exemplary embodiment of the invention, inwhich four series arrays are formed.

Referring to FIG. 43, light emitting cells LEC are connected to eachother by interconnections to form four series arrays, which areconnected to each other in parallel between a first electrode pad 239 aand a second electrode pad 239 b. Light emitting cells having a largerarea than light emitting cells within the series arrays may be disposedat opposite ends of the series arrays. In this embodiment, two lightemitting cells are provided to the first electrode pad 219 a and onelight emitting cell is provided to the second electrode pad 219 b.However, it should be understood that the present invention is notlimited thereto and various numbers of light emitting cells may beprovided to the opposite ends of the series arrays.

On the other hand, some of the light emitting cells LEC within adjacentseries arrays are connected to each other by a common cathode 237 b, andsome of the light emitting cells are connected to each other by a commonanode 237 a. In addition, interconnections 237 including the commoncathode 237 b and the common anode 237 a may connect adjacent lightemitting cells to each other. Locations of the common cathode 237 b andthe common anode 237 a are indicated by dotted lines. As described withreference to FIG. 40, the light emitting cells 2LEC including the commoncathode 237 b or the common anode 237 b may share the first conductivetype semiconductor layer 223. Furthermore, all adjacent light emittingcells between the respective series arrays may share the firstconductive type semiconductor layer 223. For example, in thisembodiment, first light emitting cells, second light emitting cells andthird light emitting cells in the respective series arrays may share thefirst conductive type semiconductor layer 223.

Although this embodiment has been illustrated as having three lightemitting cells arranged in each series array, the number of lightemitting cells in the series array is not particularly limited so longas the series array includes one or more light emitting cells.

Although the invention has been illustrated with reference to someembodiments in conjunction with the drawings, it will be apparent tothose skilled in the art that various modifications and changes can bemade to the invention without departing from the spirit and scope of theinvention. Further, it should be understood that some features of acertain embodiment may also be applied to other embodiments withoutdeparting from the spirit and scope of the invention. Therefore, itshould be understood that the embodiments are provided by way ofillustration only and are given to provide complete disclosure of theinvention and to provide thorough understanding of the invention tothose skilled in the art. Thus, it is intended that the invention coverthe modifications and variations provided they fall within the scope ofthe appended claims and their equivalents.

What is claimed is:
 1. A light emitting diode, comprising: lightemitting cells disposed on a substrate, each of the light emitting cellscomprising: a first semiconductor layer; a second semiconductor layer;an active layer disposed between the first semiconductor layer and thesecond semiconductor layer; and a transparent electrode layer disposedon the second semiconductor layer, wherein the first and secondsemiconductor layers have different conductivity types; andinterconnections connecting the light emitting cells to each other,wherein: the interconnections comprise a common cathode commonlyconnecting first and second light emitting cells of the light emittingcells; the first and second light emitting cells share the firstsemiconductor layer; the transparent electrode layer is continuouslydisposed between the first and second light emitting cells; and thecommon cathode is electrically connected to the first and second lightemitting cells through the transparent electrode layer.
 2. The lightemitting diode of claim 1, further comprising a current blocking layerdisposed between the common cathode and the first and second lightemitting cells, wherein the current blocking layer insulates thetransparent electrode layer from side surfaces of the two light emittingcells.
 3. The light emitting diode of claim 2, wherein the currentblocking layer is wider than the common cathode.
 4. The light emittingdiode of claim 2, wherein the current blocking layer comprises adistributed Bragg reflector.
 5. The light emitting diode of claim 4,wherein a portion of the current blocking layer extends outside theshared first semiconductor layer.
 6. The light emitting diode of claim5, wherein the transparent electrode layer covers the portion of thecurrent blocking layer extending outside the shared first semiconductorlayer.
 7. The light emitting diode of claim 1, wherein theinterconnections further comprise a common anode commonly connecting thefirst and second light emitting cells.
 8. The light emitting diode ofclaim 6, wherein the interconnections further comprise aninterconnecting section connecting the common cathode and the commonanode.
 9. The light emitting diode of claim 1, wherein: the lightemitting cells comprise first and second serial arrays connected by theinterconnections; and the first and second serial arrays are connectedto each other in parallel.
 10. A light emitting diode, comprising: afirst light emitting cell and a second light emitting cell separatedfrom each other on a substrate; a first transparent electrode layerelectrically connected to the first light emitting cell; aninterconnection electrically connecting the first light emitting cell tothe second light emitting cell; and a first insulation layer disposed onthe first and second light emitting cells, wherein: the firsttransparent electrode layer is disposed on an upper surface of the firstlight emitting cell and partially covers a side surface of the firstlight emitting cell; and the first insulation layer separates the firsttransparent electrode layer from the side surface of the first lightemitting cell.
 11. The light emitting diode of claim 10, furthercomprising a second insulation layer disposed between theinterconnection and the upper surface of the first light emitting cell.12. The light emitting diode of claim 11, wherein the second insulationlayer comprises the same material as the first insulation layer.
 13. Thelight emitting diode of claim 11, wherein: the second insulation layeris disposed under the first transparent electrode layer; and theinterconnection is connected to the first transparent electrode layer.14. The light emitting diode of claim 10, wherein the first transparentelectrode layer covers three side surfaces of the first light emittingcell.
 15. The light emitting diode of claim 14, wherein a portion of thefirst transparent electrode layer partially covers a side surface of thesecond light emitting cell.
 16. The light emitting diode of claim 10,wherein: each of the first and second light emitting cells comprises alower semiconductor layer, an upper semiconductor layer, and an activelayer disposed between the lower semiconductor layer and the uppersemiconductor layer; the first transparent electrode layer iselectrically connected to the upper semiconductor layer; and a first endof the interconnection is electrically connected to the firsttransparent electrode layer and a second end of the interconnection iselectrically connected to the lower semiconductor layer of the secondlight emitting cell.
 17. The light emitting diode of claim 16, whereinthe interconnection is directly connected to the first transparentelectrode layer without an insulating material disposed over theentirety of an overlapping region therebetween.
 18. The light emittingdiode of claim 17, further comprising a second insulation layer disposedon the upper semiconductor layer of the first light emitting cell,wherein the second insulation layer is disposed below a region to whichthe first transparent electrode layer and the interconnection areconnected to the upper semiconductor layer of the first light emittingcell.
 19. The light emitting diode of claim 16, wherein the first lightemitting cell and the second light emitting cell comprise the samestructure.